(CNN) -- In soccer, bodies may not collide as much as in American football -- but the game is still not a walk in the park.

Research from Europe, where soccer is king, shows most elite players eventually pay a price for repeatedly striking the ball with their heads, a legal move known as "heading."

Dr. David Janda of the Institute for Preventative Sports Medicine said drills where players repeatedly bounce the ball off their heads may leave some briefly dizzy, seeing double or even nauseous -- symptoms leading up to mild concussions.

In the lab, he measured the speed and impact of a flying soccer ball and followed up with field studies of how repeated heading might affect memory and thinking ability.

"Our studies tell us that even in the younger group -- 11, 12, 13, 14 years of age -- we do start to see some reduction in information processing and memory deficits," he said. "But we feel that it is not permanent."

Janda suggests using small beach balls for heading drills and urges all players to sit out if heading makes them dizzy or ill.

But Ronnie Pascale, a 19-year veteran of the sport, does not see heading as a problem.

"I've never seen any direct hazards from heading," said Pascale, who currently plays with the minor league professional soccer team the Atlanta Silverbacks. "I've been heading the ball since I was 4 years old. I think I'm okay."